Wrap adjust device for controlling engagement between a web and roller in an imaging system

ABSTRACT

The temperature of a heat sensitive web is controlled by varying the contact area between the web and a thermo roller having an appropriate thermo energy device coupled to it. A wrap adjust roller is supported for movement along a circular path concentric with the periphery of the thermo roller and varies the surface area contact between web and thermo roller at different locations relative to the thermo roller.

United States Patent 1191 178/6.6 TP; 340/173 TP; 34/110, 152;

Kingsley et al. 1 1 March 6, 1973 WRAP ADJUST DEVICE FOR [56] ReferencesCited CONTROLLING ENGAGEMENT BETWEEN A WEB AND ROLLER IN AN UNITEDSTATES PATENTS IMAGING SYSTEM 3,113,179 12/1963 Glenn ..l78/6.6 TP

2,788,587 4/1957 Dsenis ..34/1l0 [75] Inventms K'ngsleyi when R All,3,246,400 4/1966 Brown ..34/110 of Rmhester, 3,328,776 6/1967 Hughes etal. ..346/74 '1? [73] Assignee: Xerox Corporation, Stamford,

Conn Primary Examiner-Bernard Konick Assistant Examiner.lay P. Lucas[22] F'led: 1971 Attorney-James J.Ra1abate et a1. [21] App1.No.: 171,819

[57] ABSTRACT [52] US, Cl ,346/74 TP, 165/89, l78/6 6 TPR, Thetemperature of a heat sensitive web is controlled 346/74 MT by varyingthe contact area between the web and a [51] Int. Cl. ..H04n 5/82 rmoroller having an appropriate thermo energy I [58] Field of Search..346/74 TP, 74 MT, 77 E; device coupled to it. A wrap adjust roller issupported for movement along a circular path concentric with theperiphery of the thermo roller and varies the surface area contactbetween web and thermo roller at different locations relative to thethermo roller.

7 Claims, 4 Drawing Figures PATENTEUHAR 6197s 3,719,951

SHEET 10F 2 INVENTORS ROBERT F. ALL! 5 KINSLEY 742 AUTO/Wk PATEf-HEEHARSW73 3,719,951

SHEET 2 BF 2 FIG. 3

WRAP ADJUST DEVICE FOR CONTROLLING ENGAGEMENT BETWEEN A WEB AND ROLLERIN AN IMAGING SYSTEM BACKGROUND OF THE INVENTION temperature. Thetemperature control is used to process a heat sensitive image recordingmember in web form.

A migration imaging system is disclosed in U.S. Pat. No. 3,520,681 andcopending applications Ser. No. 553,837, filed May 31,1966 nowabandoned, 634,757, filed Apr. 25, 1967 now abandoned; and 837,791,filed June 30, 1969 now U.S. Pat. No. 3,580,962 and the disclosures ofthe foregoing are incorporated herein by reference. Broadly, the abovemigration imaging system employs an imaging member including imageparticles and a softenable material. Electric forces associated withcertain of the image particles cause the particles to migrate throughthe softenable material when its mechanical resistance to the migrationis reduced. The mechanical resistance of the softenable material isreduced by methods including softening, heating, exposing to solventvapors or liquids and combinations of the foregoing. The presentinvention is concerned with heating and cooling the foregoing imagingmembers and other heat sensitive members in web form. I

A migration imaging member in web form may be heated as part of adevelopment step for forming a visible image. The same film is alsocooledto lock particles at specified locations within the film. Withother heat sensitive materials, heating and cooling may serve some otherpurpose. The problem in each case is how to control the exchange ofenergy with a web without raising or lowering thetemperature of the webto a level at which the member is structurally and/or functionallydamaged.

Accordingly, it is an object of this invention to overcome theabove-noted problems and limitations.

Specifically, it is an object of the present invention to devise methodsand apparatus for exchanging thermoenergy with the above referencedmigration imaging member in web form.

Another object of the instant invention is to protect a heat sensitiveweb from being heated or cooled to temperatures that are structurally orfunctionally unsuitable.

Yet another object of the invention is to effect rapid engagement anddisengagement ofv a thermo-energy element with a web member.

Still another object of this invention is to control the surface areaover which thermo-energy is exchanged with a web.

Even a further object of the instant invention is to contact a web witha thermo-energy device while the web is moving and to break the contactwhen the web is stationary.

These and other objects of the present invention are realized with novelweb handling methods and apparatus. Thermo-energy is exchanged with aweb member by passing the web over a thermo roller coupled to athermo-energy device. A first heat exchange occurs while the web is in.contact with the thermo roller and a second heat exchange is made whenthe web is separated from the roller. The engagement and separation ofthe web and thermo roller is accomplished with a wrap adjust device. Thewrap adjust device includes a wrap roller journaled in pivot arms thatare rotatably supported about the rotation axis of the thermo roller.The wrap roller moves around the periphery of the thermo roller along acoincident circular path. The position of the wrap roller relative tothe thermo roller determines whether the web is in contact with thethermo roller and the amount of surface area contact between them.

DESCRIPTION OF THE DRAWINGS Other objects and features of the instantinvention will be apparent from a further reading and from the drawingswhich are:

FIG. 1 is a schematic perspective view of an imaging system includingweb handling methods and apparatus according to the present invention.

FIGS. 2-4 are schematic side elevation views of a web passed over wrapand thermo rollers with the wrap roller at a different position in eachfigure illustrating different areas of contact between the thermo rollerand web including no contact.

DESCRIPTION The migration imaging system of FIG. 1 employs a thermoroller 1 and wrap adjust device 2 for controlling the temperature of web3. Web 3 is a migration imaging structure including a conductivesubstrate and a migration layer composed of image particles andsoftenable material. The web is threaded through the machine between thesupply 4, and take-up reel 5. Images are formed with the web as it iswound between the two reels by steps including: depositing electrostaticcharge on the free or outer surface of the web as it travels pastcorotron 9; exposing the charged web to electromagnetic radiation (forexample, a flying light spot) as it travels past exposure means Ill; anddeveloping the charged and exposed web as it moves past the thermoroller by reducing the mechanical resistance of the web softenablematerial to migration by the image particles. The reduction inmechanical resistance may be effected by several methods including thepresently concerned method of heating the softenable material.

The charging and exposing steps give rise to a latent electrical imagewhich is rendered visible by development at the thermo roller. Solventvapor and/or liquids may be used in addition to the heat. The heatingreduces the mechanical resistance of the web by softening it. The imageparticles associated with the latent electrical image migrate in depththrough the developed softenable material thereby creating positive andnegative images from the migrated and nonmigrated particles. Processparameters such as charge levels, polarities and/or materials arecontrollable such that the exposed or the non-exposed particles are theimage particles that migrate. For details in regard to the migrationimage process, the reader is directed to the initially referenced Patentand Patent Applications. These references also include disclosuresrelating to washing away the softenable material and to splitting asoftenable material to separate migrated and nonmigrated particles.

placed on a photoconductor, the process step can include charging,exposing and developing as with the migration imaging process. Thedifference between the processes include those involved in thedeveloping step. In one developing step, particles migrate and in theother a surface deforms.

Heating and/or cooling web members is desirable in systems other thanthe foregoing. For example, a silver halide motion picture film requirescooling to protect the resin material of the film from heat generated bylamps used to project the film images. In addition, the manufacture ofweb members may include a step wherein heat is applied to or subtractedfrom a web for diverse purposes. The present invention finds use in allsuch web systems, processes and/or apparatus.

Turning now to FIG. 1, horizontal and vertical frame plates 14 and 15support the various system components. The drive mechanism 16 isillustrated in an ex ploded position adjacent the vertical frame plateon which it is carried. The drive mechanism includes the electric motor17 drivingly coupled to the take-up reel 5 and the drag brake or clutch18 coupled to supply reel 4. The motor coupled to the take-up reel pullsthe web 3 from the supply reel against the bias force provided by thedrag brake to maintain tension in the web whether it is moving or atrest. The web is threaded under the first idle roller 19 and over theimage roller 20. From the image roller, the web is threaded: around thethermo roller 1 and wrap adjust device 2; over the exit idle roller 21;across the display idle rollers 22 and 23 and viewing screen 24; andonto the take-up reel 5. As mentioned earlier, the web is charged as itpasses corotron 9, exposed as it traversed means 10 and developed as itpasses the thermo roller 1.

The corotron includes a thin conductive wire coupled to a highelectrical potential source. The web substrate is conductive and iscoupled to a suitable potential, e.g. ground, through the image roller20. The image roller is a conductive roller electrically coupled toground, for example, to ground the web. The potential difference betweenthe web substrate and corotron wire yields a flow of ions and othercharged particles between them. Consequently, the outer surface of theweb is charged to a high potential by the ions and other chargedparticles deposited on its surface.

The exposure mechanism is illustrated schematically as a moving pencilof electromagnetic radiation 30 that sweeps across the width of the web.This pencil of light can be generated by any suitable means including abeam of light reflected from the mirror surface of a galvanometer. Theintensity of the light beam can be modulated by suitable means such as atransparency positioned in its path. The light beam may be thatgenerated at the face of a cathode ray tube. Alternately, the exposuremeans can include a line or slit exposure wherein a line of lightreplaces the pencil of light 30.

The thermo-roller includes a relatively large diameter roller having anappropriate heating (or cooling in another system) element within itsvolume. Examples of suitable thermo energy elements include: anelectrical resistance heater; and infra-red lamp; hot or cold liquidcoils; and hot or cold vapor coils. The object is to exchange thermoenergy between the web and the periphery of the thermo roller. Mostconveniently, the thermo roller periphery is heated or cooled byconduction through the walls of the roller. How the walls are heated isnot particularly important since this may be a matter of designconvenience. For example, radiation and/or convection may be theprincipal means for heating the inside walls of the roller. However,this invention is not limited to the methods of heating or cooling sincethe invention may be practiced even when the thermo-roller is a hollowglass cylinder having an infrared lamp within its volume. The primaryrequirement for this invention is to provide a web location at which ahighly efficient heat transfer occurs. This location is the periphery ofthe thermo-roller and the wrap adjust device cooperates to control webtemperature by varying the contact area between the web and thermoroller.

The wrap adjust device includes two pivot arms journaled at oppositeends of the thermo roller about its axis. Member 40 is one of the pivotarms and is typical of the other positioned at the hidden (as viewed inFIG. 1) end of the thermo-roller. A wrap adjust roller 41 is journalednear the free ends of the pivot arms by suitable bearings, bearing 42being typical. A lock nut 43 is coupled to the axle of the thermo rollerand abuts against pivot arm 40 to hold it against rotation. When thelock nut is loosened, the pivot arms are rotated to vary the location ofthe wrap adjust roller relative to the thermo roller. With this scheme,the wrap roller can be positioned at an infinite number of locations ona circular path around the thermo roller. The clearance between theperipheries of the wrap adjust and thermo rollers is selected to besufficiently great to prevent contact between the web and thermo rollerat least at one position of the wrap roller. The function of webseparation is discussed in more detail below.

The lock nut 43 is representative of one of many mechanisms forcontrolling the position of the wrap adjust roller relative to theperiphery of the thermo roller. In more sophisticated systems, the locknut is replaced by a stepping motor or other position control device.The position control device is operated automatically in response to themovement of the web. An example, is an electrical motor coupled to thepivot arms that is energized to rotate in a first direction a fixednumber of angular degrees when the motor 17 coupled to the take-up reel5 is started and a fixed number of angular degrees in the oppositedirection when motor 17 is stopped. Switching apparatus capable of suchoperation is well known. The described apparatus causes the web to bepulled into contact with the periphery of the thermo roller when the webmoves and to be pulled out-of-contact with the thermo roller when theweb stops.

FIGS. 2-4 depict the operation of the wrap adjust device except thepivot arms are deleted for clarity of presentation. The angle theta isthe angle by which the web 3 is diverted when passed around the thermoroller while out of contact with the wrap adjust roller M. The angletheta also defines the maximum contact area between the thermo rollerand web. The larger the angle theta, the greater the amount of heatexchange occurs between the web and thermo roller because of the greaterperiod of time in which heat is exchanged.

The angle theta also defines the minimum dimension for the pivot radius50 which is the distances between the axes of rotation of the wrapadjust and thermo rollers. When the radius 50 is sufficient to positionthe wrap adjust roller near the apex of angle 50, a minimum contactoccurs between the web and thermo roller. Making the radius 50 evenlarger to position the wrap roller to the right of the apex of angletheta, as in FIG. 4, results in complete separation between the web andthermo roller. The drag brake 18 coupled to the supply reel keeps theweb taut when the wrap roller is positioned at either the home positionshown in FIG. 2 or the apex position shown in FIG. 4.

If the thermo roller is heated (versus cooled), the temperature of theweb is raised when roller 41 is at the home position. The webtemperature is lowered by the ambient air when the wrap roller islocated at the apex position. The surface contact can be varied betweenthe two extremes by locating the wrap roller at intermediate positionssuch as illustrated inFlG. 3.

The angle theta is selected for the needs ofa particular system and maybe varied from zero degrees to 180. In the event that theta'is zerodegrees, the web is wrapped half way around the thermo roller and theradius of the wrap roller must be greater than the radius of the thermoroller to obtain complete separation between the web and thermo roller.The apex position in this case is at infinity. When theta is 180, thecontact between the web is substantially a line at the tangent pointbetween the web and thermo roller. The wrap roller separates the twowhen positioned at the apex of angle theta, in this case the tangentpoint. Alternately,-the wrap roller is positioned on the other side ofthe web. In this case, there is minimum surface contact when the wraproller is at the apex or tangent point and the contact area is increasedwhen the roller is moved to another position. Since the web is betweenthe wrap and thermo roller, the wrap roller pulls the web into greatercontact with the thermo'roller when moved from the apex position.

Other variations and embodiments'of this invention will be apparent tothose skilled in the art from the present description and drawings.

What is claimed is:

l. A method of controlling the temperature of a heat sensitive web,including a migration imaging member comprising imaging particles and asoftenable material, comprising depositing electrostatic charge on saidweb and exposing said web to electromagnetic radiation in imageconfiguration to create an electrical latent image which develops byimagewise migration of image particles as a result of the contact ofsaid web with a thermo roller having a thermo energy source includingmeans for heating the thermo roller, coupled to it;

wrapping said web about the thermo roller thus diverting the directionofthe web;

supporting a wrap adjust roller for movement along at least a portion ofcircular path around the periphery of the thermo roller;

moving the said wrap adjust roller between at least two positions onsaid circular path for varying the surface area contact between the weband the thermo roller.

2. A method of controlling the temperature of a heat sensitive web,including a thermoplastic deformation member including a thermoplasticinsulating layer and a photoconductive layer, comprising:

depositing electrostatic charge on said web and exposing said web toelectromagnetic radiation in image configuration to create an electricallatent image which develops by imagewise deforming said insulating layeras a result of the contact of said web with a thermo roller having athermo energy source, including means for heating the thermo roller;

wrapping said web about the thermo roller thus diverting the directionof the web;

supporting a wrap adjust roller for movement along at least a portion ofa circular path around the periphery of the thermo roller;

moving said wrap adjust roller between at least two positions on saidcircular path for varying the surface area contact between the web andthermo roller.

3. Imaging apparatus comprising:

a. means for advancing a member comprising a web through a predeterminedpath;

b. charging means positioned along said path adapted to charge saidmember;

c. exposure means positioned along said path adapted to expose themember to an image configuration of electromagnetic radiation to createan electrical latent image in said member;

(1. development means comprising a thermo roller positioned along saidpath adapted to have the member wrapped around a portion of itsperiphery to effect heat exchange between the member and said thermoroller;

e. a wrap adjust roller supported for movement along a circular patharound the periphery of said thermo roller for varying the surface areacontact between the member and said thermo roller.

4. Imaging apparatus comprising supply and take up reels for supportinga heat developable imaging web,

an imaging roller positioned adjacent said web between the supplyandtake up reels for electrically coupling a potential source to aconductive substrate of said web,

a corotron for generating electrostatic charge for deposition onto saidweb as it passes the imaging roller,

exposure means for exposing a charged web to elec tromagnetic radiation,

a thermo roller positioned to have said web wrapped around a portion ofits periphery for heating the web for image development and a wrapadjust roller supported for movement along a circular path around theperiphery of said thermo roller for varying the surface area contactbetween the web and thermo roller.

control device includes switching means for moving said wrap adjustroller to a position causing contact between the web and thermo rollerwhen the web is moving between the supply and take up reels and to aposition for separating the web from the thermo roller when the web isat rest.

1. A method of controlling the temperature of a heat sensitive web,including a migration imaging member comprising imaging particles and asoftenable material, comprising depositing electrostatic charge on saidweb and exposing said web to electromagnetic radiation in imageconfiguration to create an electrical latent image which develops byimagewise migration of image particles as a result of the contact ofsaid web with a thermo roller having a thermo energy source includingmeans for heating the thermo roller, coupled to it; wrapping said webabout the thermo roller thus diverting the direction of the web;supporting a wrap adjust roller for movement along at least a portion ofcircular path around the periphery of the thermo roller; moving the saidwrap adjust roller between at least two positions on said circular pathfor varying the surface area contact between the web and the thermoroller.
 1. A method of controlling the temperature of a heat sensitiveweb, including a migration imaging member comprising imaging particlesand a softenable material, comprising depositing electrostatic charge onsaid web and exposing said web to electromagnetic radiation in imageconfiguration to create an electrical latent image which develops byimagewise migration of image particles as a result of the contact ofsaid web with a thermo roller having a thermo energy source includingmeans for heating the thermo roller, coupled to it; wrapping said webabout the thermo roller thus diverting the direction of the web;supporting a wrap adjust roller for movement along at least a portion ofcircular path around the periphery of the thermo roller; moving the saidwrap adjust roller between at least two positions on said circular pathfor varying the surface area contact between the web and the thermoroller.
 2. A method of controlling the temperature of a heat sensitiveweb, including a thermoplastic deformation member including athermoplastic insulating layer and a photoconductive layer, comprising:depositing electrostatic charge on said web and exposing said web toelectromagnetic radiation in image configuration to create an electricallatent image which develops by imagewise deforming said insulating layeras a result of the contact of said web with a thermo roller having athermo energy source, including means for heating the thermo roller;wrapping said web about the thermo roller thus diverting the directionof the web; supporting a wrap adjust roller for movement along at leasta portion of a circular path around the periphery of the thermo roller;moving said wrap adjust roller between at least two positions on saidcircular path for varying the surface area contact between the web andthermo roller.
 3. Imaging apparatus comprising: a. means for advancing amember comprising a web through a predetermined path; b. charging meanspositioned along said path adapted to charge said member; c. exposuremeans positioned along said path adapted to expose the member to animage configuration of electromagnetic radiation to create an electricallatent image in said member; d. development means comprising a thermoroller positioned along said path adapted to have the member wrappedaround a portion of its periphery to effect heat exchange between themember and said thermo roller; e. a wrap adjust roller supported formovement along a circular path around the periphery of said thermoroller for varying the surface area contact between the member and saidthermo roller.
 4. Imaging apparatus comprising supply and take up reelsfor supporting a heat developable imaging web, an imaging rollerpositioned adjacent said web between the supply and take up reels forelectrically coupling a potential source to a conductive substrate ofsaid web, a corotron for generating electrostatic charge for depositiononto sAid web as it passes the imaging roller, exposure means forexposing a charged web to electromagnetic radiation, a thermo rollerpositioned to have said web wrapped around a portion of its peripheryfor heating the web for image development and a wrap adjust rollersupported for movement along a circular path around the periphery ofsaid thermo roller for varying the surface area contact between the weband thermo roller.
 5. Apparatus according to claim 4 wherein saidexposure means is adapted for exposing a charged web to an imageconfiguration of electromagnetic radiation.
 6. The apparatus of claim 4further including position control means coupled to said wrap adjustroller for moving the wrap adjust roller between various positions alongsaid circular path.